How hard is it to sail around the world? I guess it's probably as hard as it is to climb Mt. Everest, but spread out over a period of 8 months or more, rather than a couple of days.
If one is an intelligent singlehander (or cruiser, for that matter) shouldn't one tuck a reef or two before dark, be aware enough of what's going on around you to be in control before most situations escalate, be in a mental state conducive to the intended voyage and have a vessel up to the trip?
It is amazingly tiring to spend a protracted amount of time at sea, but it shouldn't be hard work. With modern rigs, cockpit sail controls (halyards, reefing, etc.), roller furling, lazy jacks and the electronics most of us use, the difficulty factor has gone from ironman status to something a teenager can do (hey, a blind guy sailed to Hawaii).
Most of us would not sail in the Roaring 40's, the Furious Fifties or the Shrieking/Screaming Sixties; we'd choose the lower latitudes and the seasons, with attention to things like hurricanes, monsoons and the proper time of year for the cape transits.
Hard, not so much. Preparation, commitment and planning, more so.